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Regional Anesthesia Technique Significantly Improves Outcomes of Hip and Knee Replacement Surgery

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Comparative Effectiveness Research Identifies Anesthesia Technique That Has Lower Rates of Complications

NEW YORK (May 1, 2013) — A highly underutilized anesthesia technique called neuraxial anesthesia, also known as spinal or epidural anesthesia, improves outcomes in patients undergoing hip or knee replacement, according to a new study by researchers at Hospital for Special Surgery and Weill Cornell Medical College. The study, which appears in the May issue of the journal Anesthesiology, found that neuraxial anesthesia, a type of regional anesthesia, reduced morbidity, mortality, length of hospital stay and costs when compared with general anesthesia.

"The influence that the type of anesthetic can have on perioperative outcomes has been vastly underestimated. Indeed, our study suggests that the type of anesthesia chosen may have important impacts on all kind of medical and economic outcomes in orthopedic surgical patients," says Dr. Stavros Memtsoudis, director of Critical Care Services at Hospital for Special Surgery and clinical professor of anesthesiology and clinical professor of public health at Weill Cornell Medical College. "It is not something to be taken lightly."

The findings of this comparative effectiveness research could be applied to more than one million patients undergoing joint arthroplasty in the United States each year.

Using neuraxial anesthesia over general anesthesia reduced the risk of pulmonary compromise by twofold in knee replacement patients and more than threefold in hip replacement patients. "When one considers the modest decrease in risk of adverse outcomes associated with the use of a number of widely used medications such as anti-cholesterol drugs, the effect sizes seen in this study are really impressive," says Dr. Memtsoudis.

Neuraxial anesthesia involves injecting medication into fatty tissue that surrounds the nerve roots in the spine (known as an epidural) or into the cerebrospinal fluid that surrounds the spinal cord. Currently, the majority of joint replacements in the United States are performed under general anesthesia. Anesthesiologists at Hospital for Special Surgery, however, use regional anesthesia for more than 90 percent of hip and knee replacements. In the past, several small studies have shown that compared with general anesthesia, regional anesthesia reduces intraoperative blood loss and the need for blood transfusions.

In the new study, researchers at Hospital for Special Surgery conducted a retrospective review of hip and knee replacements performed between 2006 and 2010 in the United States using data collected by Premier Perspective. This administrative database contains discharge information from approximately 400 acute care hospitals located throughout the United States.

Information on the type of anesthesia used was available in 71.4 percent of 528,495 patients. Eleven percent received neuraxial anesthesia, 14.2 percent received combined neuraxial and general anesthesia and 74.8 percent received general anesthesia. Thirty-day mortality was significantly higher in patients who received general anesthesia, 0.18 percent, compared with those who received neuraxial, 0.10 percent, or neuraxial-general, 0.10 percent.

"Other studies have suggested some benefit of neuraxial over general anesthesia, but they looked at very limited outcomes, primarily at risk of bleeding and blood transfusions. What this study does for the first time is really explore the impact of anesthesia on a wider range of important outcomes," says Dr. Memtsoudis. "We found lower rates of complications including pulmonary compromise, pneumonia, infections and acute renal failure when neuraxial anesthesia is used. The choice of anesthesia seemed to basically affect every organ system."

When patients who received general anesthesia were compared to patients who received neuraxial or a combination of neuraxial and general, they were found to have higher rates of pulmonary compromise (0.81 percent vs. 0.37 percent vs. 0.61 percent), infections (4.5 percent vs. 3.11 percent vs. 3.87 percent) and acute renal failure (1.75 percent vs. 1.1 percent vs. 1.43 percent).

Neuraxial anesthesia was also associated with shorter hospital stays and lower health care costs. Patients were defined as having a prolonged hospital stay if they fell in the 75th percentile of the study cohort in terms of stay duration. The researcher found that more patients receiving general anesthesia (35.4 percent) had a prolonged hospital stay than patients who received neuraxial (28.7 percent) or neuraxial and general (27.4 percent). Patients were less likely to fall into the upper 75th percentile in terms of health care costs if they received neuraxial anesthesia (21.4 percent) or combined neuraxial-general (18.3 percent) than in the general anesthesia group (23.4 percent). "Patients were 30 percent more likely to be in the group that had the highest costs if they received general anesthesia alone," says Dr. Memtsoudis.

Anesthesia medications used during surgeries are a small fraction of overall health care costs, and the costs of regional and general anesthesia are similar.

Dr. Memtsoudis pointed out that educating patients is key. "Some patients don't like the idea of having an injection in their back and their legs being numb, but a thorough discussion of risks, benefits and alternatives can go a long way to help an educated patient make rational decisions," he says. "For the anesthesiologist, a number of factors come into play, including patient comorbidities and preferences as well as other practice specific factors, such as the choice for anticoagulation, but regional anesthesia should, at the very least, be considered in every patient."

While randomized clinical trials are the gold standard of clinical research, such trials are not feasible for testing anesthesia technique in joint replacement surgeries because the low incidence outcomes would require a huge number of patients.

The study was performed with funds from the Department of Anesthesiology at Hospital for Special Surgery and the Anna-Maria and Stephen Kellen Physician-Scientist Career Development Award, New York (Stavros G. Memtsoudis). Contribution of Drs. Mazumdar and Banerjee, Ms. Chiu, and Ms. Sun on this project was supported in part by funds from the Clinical Translational Science Center, New York, and the National Center for Advancing Translational Sciences, Rockville, Md.

Other investigators involved in the research include Dr. Ottokar Stundner and Nigel Sharrock from Hospital for Special Surgery; Dr. Spencer Liu, formerly from HSS and now at the University of Washington; and Dr. Samprit Banerjee, Xuming Sun, Ya-Lin Chiu, and Dr. Madhu Mazumdar from Weill Cornell Medical College.

Hospital for Special Surgery

Founded in 1863, Hospital for Special Surgery (HSS) is a world leader in orthopedics, rheumatology and rehabilitation. HSS is nationally ranked No. 1 in orthopedics, No. 3 in rheumatology, No. 10 in neurology and No. 5 in geriatrics by U.S. News & World Report (2012-13), and is the first hospital in New York State to receive Magnet Recognition for Excellence in Nursing Service from the American Nurses Credentialing Center three consecutive times. HSS has one of the lowest infection rates in the country. From 2007 to 2011, HSS has been a recipient of the HealthGrades Joint Replacement Excellence Award. HSS is a member of the NewYork-Presbyterian Healthcare System and an affiliate of Weill Cornell Medical College and as such all Hospital for Special Surgery medical staff are faculty of Weill Cornell. The hospital's research division is internationally recognized as a leader in the investigation of musculoskeletal and autoimmune diseases. Hospital for Special Surgery is located in New York City and online at www.hss.edu.

Weill Cornell Medical College

Weill Cornell Medical College, Cornell University's medical school located in New York City, is committed to excellence in research, teaching, patient care and the advancement of the art and science of medicine, locally, nationally and globally. Physicians and scientists of Weill Cornell Medical College are engaged in cutting-edge research from bench to bedside, aimed at unlocking mysteries of the human body in health and sickness and toward developing new treatments and prevention strategies. In its commitment to global health and education, Weill Cornell has a strong presence in places such as Qatar, Tanzania, Haiti, Brazil, Austria and Turkey. Through the historic Weill Cornell Medical College in Qatar, the Medical College is the first in the U.S. to offer its M.D. degree overseas. Weill Cornell is the birthplace of many medical advances — including the development of the Pap test for cervical cancer, the synthesis of penicillin, the first successful embryo-biopsy pregnancy and birth in the U.S., the first clinical trial of gene therapy for Parkinson's disease, and most recently, the world's first successful use of deep brain stimulation to treat a minimally conscious brain-injured patient. Weill Cornell Medical College is affiliated with NewYork-Presbyterian Hospital, where its faculty provides comprehensive patient care at NewYork-Presbyterian Hospital/Weill Cornell Medical Center. The Medical College is also affiliated with the Methodist Hospital in Houston. For more information, visit weill.cornell.edu.

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